Unknown High Frequency Distortion, Recording or Speaker?


I just upgraded to Audioengine's HD6 power speaker, from the much smaller A2+. My expectation was that since the drivers are bigger and not only with far more power, but dual amps, that it would produce better mid-range and have more detailed treble. In many ways it has...but I am noticeing a weird high frequency grain-like distortion.  Like something is vibrating at a high frequency, smearing the details. Thus far, I have only heard it on two songs that I test with:

Billy Joel's "New York State of Mind."  In this song, the piano is fine, but when he sings, it's as if he is singing through an old paper cone and the paper is vibrating, causing a grainy sound to his voice.

Journey's "Faithfully" the piano distorts in the high freqncy range, as though it was recorded beyond the 0 db range and distorting, but when Steve sings...it's fine. *shrug.*

But here's the kicker.  When I run sine waves, no issue. It will start from 20hz and cycle all the way up to 20Khz with zero distorition.

Also, the A2+ did not have these issues and the HD6 is using the exact same cables and power back end. The only thing that has changed, other than the speaker itself, are the stands.  The A2+ was on the desk with their rubber stands.  The HD6 are on metal Sanus 30" speaker stands and on spikes.

So, the question is...is there something in my system causing the distortion or is it just the recording and I never noticed because I didn't have as high a resolving speaker?

Previewguakus

When I run sine waves, no issue. It will start from 20hz and cycle all the way up to 20Khz with zero distorition.

How you measure the distortion?

Sure you're not playing them too loud? Is the distortion happening at lower volumes too? 

@imhififan 

It's a grainy scratchy sound at the high frequency. As though the speaker were blown or if you recorded the sound too loud and it was distorted.

Technically, it sounds like it's "too loud" but...it isn't and I have narrowed it down to happening on the powered speaker and not the slave speaker.

@noromance I cannot hear it at low volume, but can at middle volume and most definitely at high volume.

It does sound like the sort of distortion you get when a tweeter is too loud, but two things:

Not all songs, and this didn't occur in the smaller Audioengine A2+.  I could crank those to destructive sound levels and there would never be distortion. That was what impressed me about them.  This is their top model with more power and a larger tweeter.  It could be defective.

 

You did not say what your source is. Try attenuating the input to your pre-amp. I have found that D/A converter outputs can be too hot for a lot of pre-amps.

@johnlcnm 

The setup is as thus:

PC: Acer Helios 300 Predator
USB OUT: Audioquest Jitterbug FMJ
USB OUT: Audioquest Dragonfly Cobalt
OUT: 3.5 Stereo mini-pin to left/right RCA.

INTO: Audioengine HD6 via RCA input.

The Audioengine HD6 is a powered speaker with dual A/B class amps.

The D/A converter is the Dragonfly Cobalt.  I have tried switching to the Dragonfly Red to see if it resolves the issue, it does not. I have tried switching the left and right inputs and the issue stays with the left (powered) speaker.

What is so confounding is that on a large majority of songs, I don't get any distortion, regardless of volume level.  It only seems to happen on certain songs with certain musical characteristics and only on the left (powered) side.

I started reading reviews on Amazon (no, that isn't where I bought these) and I saw at least three complaints that the left speaker had treble distortion.

So now I wonder, if it is the actual tweeter or something messed up on circuit board?  I have read here and elsewhere that sometimes with Audioengine products, they either put far too much solder or not nearly enough.

Which would you think would cause this issue? A problem of solder or a defect in the tweeter itself?

 

I started reading reviews on Amazon (no, that isn't where I bought these) and I saw at least three complaints that the left speaker had treble distortion.

Yeah, I'd be returning those if possible. 

Which would you think would cause this issue? A problem of solder or a defect in the tweeter itself?

It's hard to say, since the electronics and transformer(s) all house in the left speaker, there’s possibility of electromagnetic interference. Although no distortion detected on large majority of songs, we can’t rule out the possibility of defective tweeter without measuring it.

 

@imhififan 

I downloaded REW Room EQ Wizard.  I don't have a good microphone, especially not one with reach once plugged into the headphone jack.

However, I did run the Tone Generator.  I isolated the Left speaker, cranked the volume and ran through the tones.  I could NOT get the speaker to distort.  At all. it very much could produce any tone at damaging levels of volume with zero distortion that I was hearing.

This is why I am confused.  Is it that the speaker is so high tuned that it picks up distortion within the recording and play it?  Does that happen?  The passive speaker just receives whatever signal the powered speaker sends it and I am unable to perceive distortion from that speaker regardless of what is playing.

 

@noromance 

*sigh* I would return them...but...I will never find these again in Cherry Wood, especially not for the price new. I lucked into these.  The guy selling them on eBay was selling at nearly 1/2 off retail because the external box was damaged.  It had a gaping hole almost dead-center.  He didn't bother to open to check the status of the speakers and just assumed they were damaged.

That hole went right between the speakers.  They were 100% untouched, undamaged. I am going to keep them, even if I have to replace the tweeter myself :)

FINAL UPDATE:

I found out the problem and it is solved.  So for internet searching posterity, here was the problem and here is how it was fixed:

Problem:
The tweeter did not have a foam surround that is meant to cushion the tweeter where it screws into the chassis. So when complex musical energy enters the tweeter it would vibrate, which caused distortion.

Solution:
I ordered a new tweeter from Audioengine.  That new tweeter had a nice, fat, foam surround.  It installed easily and no more treble distortion! :D

So, in the end, the issue was the tweeter. Looking at the old tweeter, it looks like someone ripped the foam surround off, leaving the sticky residue and bits of foam and simply connected the tweeter anyway. So, it was also a manufacturing error.

 

Glad you have it resolved 👍